Paper containing a polyethylenimine-fatty acid epichlorohydrin product

ABSTRACT

An improved polyethylenimine adduct for cellulosic products is prepared by condensing polyethylenimine with 0.05-0.4 mole of a C12-C22 fatty acid and thereafter capping the residual free amino groups by reaction in aqueous solution at 0*-50*C. with epichlorohydrin. The resulting product is an effective softener, sizing agent, and wet strength additive for paper and other cellulosic products with superior color stability and increased resistance to yellowing.

United States Patent Longoria [4511 Sept. 19, 1972 [54] PAPER CONTAININGA 2,882,185 4/1959 Valko et a1. ..260/18 N POLYETHYLENIMlNE-FATTY ACID2,926,116 2/1960 Keim ..260/29.2 EP EPICHLOROHYDRIN PRODUCT 2,962,010:1/ Green ...2.l62/l64 [72] Inventor: Juan Longoria, Lake Jackson, Tex. 3I Dickson et a 60/2 EN [73] Assignee: The Dow Chemical Company, FOREIGNPATENTS 0R APPLICATIONS Midland, Mich. 6,612,293 3/1967 Netherlands..260/2 EN [22] Flled: April 1971 Primary ExaminerS. Leon Bashore PP139,464 Assistant Examiner-Frederick Frei Related us. Application Data f[62] Division of Ser. No. 736,556, June 13, 1968, [57] ABSTRACT Animproved polyethylenimine adduct for cellulosic products is prepared bycondensing polyethylenimine CCII with 005414 mole of a circa fatty acidand thereafter capping the residual free amino groups by [58] Flew ofsearch'zolz 18 reaction in aqueous solution at 0-50C. withepichlorohydrin. The resulting product is an effective softener, sizingagent, and wet strength additive for [56] Rem'ences Cited paper andother cellulosic products with superior UNITED STATES PATENTS colorstability and increased resistance to yellowing. 2,601,597 1/1952 Daniel..162/164 8 Claims, No Drawings PAPER CONTAINING A POLYETIIYLENIMINE-FATTY ACID EPICHLOROHYDRIN PRODUCT This is a Division of applicationSer. No. 736,556

filed June 13,1968.

BACKGROUND Numerous polyamine condensation products with a wide varietyof acylating and alkylating agents including fatty acids andepichlorohydrin have been described and recommended as additives forpaper, textiles, and other cellulosic products. For example, Dudley US.Pat. No. 2,479,480 describes fatty acid condensates of water-solublethermosetting alkylenepolyamine resins while Reynolds U.S. Pat. No.2,772,969 recommends colloidal dispersions of such condensates as sizingagents for paper. Dickson e.a. U.S. Pat. 3,301,783 describes the use ofacylated polyethylenimines as corrosion inhibitors in lubricants. GermanPat. No. 717,155 describes a condensation product of polyethylenimineand stearoyl chloride useful as a softening agent and surfactant intreating textiles.

A major weakness of these and other polyamine products is the oxidativediscoloration which occurs on exposure to air, particularly in thepresence of light.

Currently the only major commercial products are thepolyamidopolyamine-epichlorohydrin polymers described by Keim U.S. Pat.Nos. 2,926,116 and 2,926,154. These resins, prepared by condensation ofa saturated aliphatic dibasic acid with an alkylenepolyamine such asdiethylenetriamine and thereafter by reaction of the polyamidopolyaminewith from 0.5-2.0 moles epichlorohydrin/secondary amino group, areeffective and widely used wet-strength additives for paper.

SUMMARY OF THE INVENTION A process has been discovered for preparing newand improved water-soluble substantive polyethylenimine derivativesuseful as an additive for cellulosic products and having superior colorstability when incorporated in such products. More specifically theprocess comprises: (A) condensing polyethylenimine with about 0.05-0. 1mole of a C -C fatty acid to yield a watersoluble aminopolyamide; andthereafter (B) capping the residual amino groups by reaction in aqueoussolution at about -50 C. with at least 0.8 mole and preferably about0.85-l.2 mole of epichlorohydrin per amino group.

The resulting polyethylenimine-fatty acidepichlorohydrin condensationproduct is a water-soluble thermosetting resin with a blend of physicaland chemical properties highly desirable for paper or textileapplications. It is stable as a -30 weight percent aqueous solution atabout pH 2.0-7.5, but cures readily when the solution or treated productis dried or made strongly alkaline. It is an effective sizing agent whenapplied to paper at a loading of at least about 0.1 weight percent,preferably about 0.5-5.0 weight percent. It can be used with alkalinepaper pulps as well as acidic or neutral pulps. In addition to impartinga high degree of water resistance, it also significantly improves thewet strength of paper and textiles. Also when applied in a lowerconcentration of about 0.05-0.50 wt.,per cent Furthermore the treatedproduct and its aqueous solutions have enhanced resistance toyellowingon aging coupled with good stability and shelf life.

REACTANTS Polyethylenimine (PEI) is a commercially availablewater-soluble cationic polymer formedby polymerization of ethylenimineas described, for example, by Ulrich U.S. Pat. No. 2,182,306 and WilsonU.S. Pat. No. 3,203,910. It is a highly branched polymer with a ratio ofprimary/secondary/tertiary nitrogens of approximately l/l.52.0/l.

Particularly desirable for use herein are the polymers prepared by anacid-catalyzed, anhydrous polymerization of ethylenimine having anaverage molecular weight of about 500-5 ,000 based on ebulliometricmethods. However, higher molecular weight polyethylenimines, includingproducts made in aqueous solution and having an average molecular weightof 100,000 or more, can also be used.

To impart the desired water resistance and softer hand, a C -C fattyacid is used. Particularly suitable are saturated C -C fatty acids suchas lauric, palmitic and stearic acids which are readily available andhave good chemical stability. Also suitable are the fatty acid mixturesavailable from the hydrogenation of tall oil, cottonseed oil or coconutoil. For some applications unsaturated G -C fatty acids such as oleicacid, linoleic acid, and tall oil can be used.

To cap the residual amino groups of the PEI-fatty acid condensate,epichlorohydrin. is the preferred reagent although epibromohydrin canalso be used. Under appropriate conditions the epihalohydrin can beformed in situ from a l,3-dihalo-2-propanol and a suitable base.

PROCESS CONDITIONS To obtain a requisite water-soluble product, about5-45 mole percent of the PEI nitrogen atoms should be amidated with theC -C fatty acid. A higher substitution yields water-insoluble productswhile a lower substitution gives products with inadequate softening andsizing properties. Generally it is preferable to amidate the PEI withabout 0.1-0.3 mole fatty acid per mole PEI nitrogen.

Amidation to give the intermediate aminopolyamide is achieved in aconventional manner by heating the polyethylenimine and fatty acid atabout l20-2l0 C. until at least percent of the theoretical water hasbeen evolved. An organic diluent such as toluene or xylene willfacilitate the reaction by removing the water azeotropically.Alternately the desired acylation can be achieved with an appropriateacyl halide as described by Reynolds e.a. U.S. Pat. No. 2,772,969.

To cap the residual PEI amino groups, the aminopolyamide is dissolved inwater and reacted with epihalohydrin under controlled condition yieldinga stable water-soluble polymer in which the amino groups are substitutedwith a propylenehalohydrin group, e.g. CH,-CHOH-CH,X where X is Br orC]. The resulting water-soluble product is stable in the halohydrin formin neutral or mildly acidic aqueous solutions, e.g. at about pH 2.0-7.5.If the solution becomes alkaline, the halohydrin groups are convertedinto epoxide form with subsequent cross-linking and in solubilization ofthe polymer.

To obtain a stable water-soluble product, crosslinking must be minimizedby reacting the aminopolyamide and epihalohydrin in aqueous solution atabout 50 C. Preferably the epihalohydrin is added gradually to a -25percent aqueous solution of the amoinopolyamide over about 0.5-2.0 hoursat 20-40 C. Sufficient epihalohydrin is required to cap at least 80 molepercent of the residual free amino groups. Therefore normally about0.85-1.20 mole of epichlorohydrin per mole of amino nitrogen is added tothe aqueous aminopolyamide solution. A larger excess of epichlorohydrinoften requires further treatment to obtain a clear stable productsolution.

High conversions are achieved by stirring the reactants at 20-50 C. for1-4 hours after complete addition of the epihalohydrin. Then, ifnecessary, the aqueous product solution is heated at about 50-100 C. toremove haziness caused by residual epihalohydrin. The resulting clearproduct solution is then cooled and if necessary the pH adjusted toabout 2-7.5, preferably to about 5-7. Such a solution containing -30 wt.percent of the polyethylenimine-fatty acid-epihalohydrin product isstable for an extended time at room temperature. However heating todryness or adding a strong base rapidly transforms the product into awaterinsoluble resin.

TREATMENT OF CELLULOSIC PRODUCTS The cationic PEI-fatty acid-Epiproducts are readily absorbed from aqueous solution by cellulosicmaterials. The amount of additive applied depends both upon the specificcellulosic product being treated and the desired properties. But ingeneral additive concentrations ranging from about 0.05-5.0 wt. percentare most useful. Optimum softness of a cotton fabric is generallyobtained with a loading of about 0.1-2.0 wt. percent and such treatmentfacilitates mechanical finishing operations as well as increases thelife and utility of the fabrics. However, optimum sizing generallyrequires a loading of about 0.52.5 wt. percent based on dry weight ofthe cellulosic product. But unlike many commercial sizing agents, thesePEI derivatives also contribute a significant degree of wet strength.

Since these additives are effective over a pH range of about 3.0-1 1.0,they can be used with alkaline paper pulps which cannot be treated withmelamine or ureaformaldehyde resins. Also these additives can be usedalone with no treatment other than drying required to develop a durabletreated product. Yet they can be used if desired in conjunction withconventional fillers and additives including rosin, clay, and calciumcarbonate.

When used as a paper additive, these PEI derivatives are preferablyadded to the pulp slurry at the beater, stock chest, headbox or otherpoint permitting adequate mixing prior to formation of the paper sheet.Alternately performed paper sheets can be sprayed or dipped in anaqueous PEI-fatty acid-EPI solution. Application in this manner is ofcourse preferred for treating textile products.

Finally drying the impregnated or treated product at about 40-150 0,preferably about -120 C, trans- 6 strength properties to the treatedproduct. The improved color stability has been established both for theaqueous product solution and for the treated cellulosic products.

The following examples illustrate further this invention. Unlessotherwise specified, all parts and percentages are by weight.

EXAMPLE 1 PEI-Fatty Acid-Epichlorohydrin Products The polyethylenimine(PEI) used in the following runs was prepared by an acid catalyzedpolymerization of ethylenimine and contained about 20-25 percenttertiary amino groups.

A. A mixture of 680 parts (3.4 mole) lauric acid, 680 parts (15.8 moles)of PEI having an average molecular weight of 1,200 and 600 parts ofxylene was heated at 150-158 C. for 1.5-2.0 hrs. with azeotropic removalof water. When 57 parts (3.2 moles) of water had been removed, themixture was cooled and the xylene stripped in vacuo leaving about 1,300parts of a light amber, viscous, water-soluble liquid amino polyamide.

About parts (1.22 mole total N basis) of the aminopolyamide was added to572 parts of water. To speed dissolution, the mixture was stirred at 70C. and then the solution containing about 15 percent solids was cooledto 25 C. Then 90.5 parts (0.98 mole) epichlorohydrin was added withstirring in 0.5-1.0 hr. After stirring another hour at 25 C., theaqueous mixture heated for 2 hrs. at 50 C. to complete the reaction andobtain a clear stable solution containing 25 percent total solids. ItspH was about 7.

' B. In like manner a series of aminopolyamides have been prepared frompolyethylenimine with an average MW ranging from 600-100,000 and avariety of C -C, 2 fatty acid including lauric, oleic, stearic and talloil acids and then capped by reaction with epichlorohydrin. Typicalproducts are shown in Tables 1 and 2.

TABLE 1 PEI-Fatty Acid-Aminopolyamides Reactants Wt. Mole Fatty RatioRatio Run PEKMW) Acid FA/PEI FA/N Product l-l I200 lauric 1.0 0.22viscous amber liquid l-2 1200 oleic 0.5 0.076 light amber liquid l-3I200 lauric 0.5 0.1l viscous amber liquid l-4 1200 tall 2.0 0.30 darkamber oil liquid -5 1200 stearic 1.0 0.15 waxy solid -6 600 stearic 2.00.30 tan waxy solid l-7 1200 lauric 2.0 0.43 tan waxy solid l-8 1200oleic 2.0 0.30 very viscous liquid l-9 I200 stearic 0.5 0.075 tan waxysolid 1-10 100,000 lauric 1.28 0.28 tan waxy solid Commercial OctinolFA-3" from Arizona Chemical Co.,

Analysis: 98.7% fatty acids, 47% polyunsaturated acids as linoleic acid,51% oleic acid, 2% saturated fatty acids.

Dried azeotropically prior to reaction with lauric acid.

TABLE 2 PEI-Fatty Acid-Epi Products Aminopolyamide Ratio Mole Ratio No.No. PEI FA Epi/PEI- PEI FA Epi (MW) FA 2-1 l-l 1200 laurie 0.905 1.00.22 0.08 2-2 l-l 1200 lauric 0.85 1.0 0.22 0.75 2-3 l-7 1200 lauric0.41 1.0 0.43 0.53 2-4 l-4 1200 tall 0.50 1.0 0.30 0.67

oil 2-5 l-8 1200 lauric 0.50 1.0 0.30 0.67 2-6 -9 1200 stearic 1.33 1.00.075 0.91 2-7 1-6 600 stearic 0.52 1.0 0.30 0.70 2-8 l-8 1200 oleic0.50 1.0 0.31 0.69

Except for the lauric acid derivative of Run 1-7 the aminopolyamides andtheir Epi reaction products gave stable clear aqueous solutions at aPEI-FA product concentration of about 10-20 wt. percent at 25 C. and aPEI-FA-Epi product concentration of about -30 wt. percent at 25 C.

EXAMPLE 2 Use as a Cellulosic Sizing Agent A. Paper handsheets were madefrom unbleached Kraft paper pulp or bleached Western Softwood sulfitepaper pulpfollowing the general procedure of TAPPI Standard T 205-58modified by using a drying cycle of 45 sec. at 120 C. and then 1 hr. at110 C. in a forced draft oven. Each test sheet was aged for 24 hours at23 C. and 60 percent relative humidity prior to testing.

The sizing of the aged test sheets is measured by clamping a weighedsheet in a holder so that a 2.54 cm diameter ring is firmly held to theupper surface at about the midsection of the test sheet. A PhotovoltReflectance Meter Model 610 (Photovolt Corporation, N.Y.) equipped witha Green Trestimulus Filter and Search Unit 610-Y is mounted with thephotocell held directly below the ring. After adjusting the meter to 100percent reflectance, the ring is filled with Shaeffers Script No. 2 inkand the sizing efficiency of the additive is determined measured by (a)the time (sec.) required for the reflectance to drop to 50 percent ofthe initial value, or (b) the percent reflectance after 1,000 sec.

B. Typical sizing results using the PEI-EFA-Epi products of Example 1and several commercial sizes with paper pulps having an initial pH os4.5, 6.5, and 8.5 are shown in Table 3. Except for PEI 2-3, thewater-insoluble product with a high fatty acid ratio, the PEI adductsare superior sizes at a loading of about 1-2 wt. percent with acid,neutral and alkaline pulps.

'% Reflectance/sec. after ink application Wt. based on dry paper pulpPEI-FA-Epi derivatives from Table 2 Rosin-alum: Conventionalrosinaluminum sulfate size Cyron Size: A stearic acid polyamide fromAmerican Cyanamid The rosin-alum size requires an acidic pulp with pHbelow 5.5

C. As a comparison with the polyamine derivatives of the prior art, asolution of 170.1 parts (0.90 mole) of tetraethylenepentamine (TEPA) in180.6 parts water was condensed with 83.3 parts (0.90 mole)epichlorohydrin as described in Dudley U.S. Pat. No. 2,479,480. Aportion of the resulting TEPA-Epi condensation product was condensedwith 0.1 mole lauric acid per mole N using xylene to azeotrope the wateras described by Dudley. A second portion was similarly acylated withstearic acid. These products were then evaluated as sizing agents asdescribed above. The results along with comparative data for the presentPEl-FA-Epi productshaving a similar lauric or stearic acid content agegiven in Table 4.

TABLE4 Comparative Sizing Tests Pulp Sizing Values: Loading of Test pl-lAdditive 0.5% 1% 1.5% 2.0%

4-1 4.5 TEPA-epi- 50%]12 50%l3 50%[2 50%!3 14-] 4.5 PEl-lauric- 50%[758%[10 78%!10 81%710 epi 3-6 4.5 PEI-stearic 50%[3 50%[147 74%(10 82%[10epi 4-3 7.5 TEPA-epi- 50%[5 50%]21 50%]28 50%!16 lauric' 4-4 7.5TEPA-epi- 50%[120 77%[10 %]10 8801/10 stearic' 3-15 8.5 PEI-lauric 50%[250%!199 8311/10 %]10 epi 3-20 8.5 PEI-stearic 50%[3 50%l200 81%!1090%!10 epi Dudley U.S. 2.479.480

EXAMPLE3 Use as a Wet Strength Additive Not only are the PEl-FA-Epiproducts of Example 1 effective sizes, but in addition to imparting ahigh degree of water resistance they also increase the wet strength ofthe treated paper and textile products. Typical results are given inTable 4.

An unbleached sulfite spruce pulp with a Canadian Standard Freeness of500 mls was used following the general procedure of TAPPI method T-403.Handsheets were prepared by TAPPl Method T-205 modified in the dryingcycle by curing in a steamheated press at 120 C. for 45 sec. and then inan oven at 105 C. for 1 hour. The test sheets were conditioned at 23 C.and 50 percent relative humidity prior to testing. After weighing, thehandsheets were soaked in water for 4 hrs., blotted to remove excesswater and tested on a Muellens Burst Tester.

Although the sizing and wet strength functions are distinctly different,note that these PEI-FA-Epi products not only are effective sizing agentswhen used at a loading of about 1.0 wt. percent or more as shown inExample 2, but also give a significant increase in wet strength atloadings as low as 0.25 percent.

EXAMPLE 4 Use as a Softening Agent For use as a softening agent forpaper or textiles, a PEl-FA-Epi product containing about 02-035 molesFA/PEI nitrogen is preferred.

A. To demonstrate the utility of the PEI-Laurie Acid- Epi Product 2-1 asa softener, lightweight paper handsheets were prepared from anunbleached sulfite pulp having a freeness of 550:50 ml C.S.F. and a pHof 7.0 diluted to a 0.11 percent pulp suspension by the generalprocedure described in Example 3. The test sheets were conditionedovernight under standard TAPPl conditions and then measured forstiffness/limpness, dry tensile strength, and water absorbency. Indetermining the stiffness mm strips of the tests sheets are cut to alength of 7.5 inch (19.0 cm) weighed and clamped horizontally so that3.0 inch (7.62 cm) protrudes beyond the clamp. The horizontal deflectionof the end of the strip is measured, the strip is turned over and thedeflection again measured. Using the average value for 6 test strips,the compound modulus of tensile and compression (E) is calculated by theformula:

E (gJCIIL m The dry tensile strength and breaking length of the teststrips were than measured using a test span of mm and a stretching speedof 1.27 cm/min.

The water absorbency was determined by TAPPl Method T-432 using a 0.1 mlwater drop and measuring the time required for it to be absorbed intothe paper.

TABLE6 Paper Softening Agents Dry Mod- H,0 break- Thick- DefleclusE,absorb. ing ness wt. tion g/cm time, length Test Additive Z,mm g A.cmX10 sec. in 6-0 None 0.113 0.156 1.28 1.487 302 5440 6-1 0.05% PEl 0.1080.152 1.858 1.142 325 5020 2-1 0.10% PEl 0.108 0.149 1.925 1.077 3225090 0.50% PEl 0.108 0.145 1.658 1.248 1000 5080 2-1 6-2 0.05% QN 0.1090.152 0.152 1.359 222 4940 0.20%0N 0.108 0.149 1.592 1.333 386 41800.50%QN 0.126 0.182 1.283 1.256 351 4090 PEI 2-1: PEl-lauric acid-EpiON: Dihydrogenated and allow dimcthyl ammonium chloride (Arquad 2HT)from Armour Industrial Chemicals "Determined after curing at 1 10C for0.5 hr.

B. A cotton broadcloth (3.8 oz/yd) was impregnated by padding with anaqueous solution of PEl 2-8 and then tumble dried in an electric dryerfor 30 min. at 80-85 C. The add-on weight was 0.54 percent on a solidsbasis. The treated broadcloth after conditioned for 18 hrs at 20 C. and65 percent relative humidity was rated by a test panel considerablysofter than a control untreated sample. Another treated cloth with anadd on of 1.56 percent was rated slightly softer than the untreatedcloth.

EXAMPLE 5 Color Stability The use of polyethylenimine and itsderivatives in many areas including paper wet strength, and dimensionalstabilization of textiles has been hindered by the tendency of thesepolymers to yellow upon aging or heating in the presence of air as inmany drying operations. A modification of TAPPl methods T452 and T217was developed using standard white broadcloth substrate. The testpolymer was applied from aqueous solution with a laboratory padder andthen the samples were given a minimal drying by heating at 80 C. for 2minute. Test samples cut from the treated cloth were then heated for 30min. at C. or C. in a forced air oven, cooled, and measured forreflectance using a Photovolt Search Unit 6l0-W with a blue KodakWratten Filter No. 49.

Typical results shown in Table 7 demonstrate the greater color stabilityof the PEl-FA-Epi products even when an unsaturated fatty acid such asTall Oil is used.

TABLE 7 Accelerated Color Stability Test Test PEI Additive 7 A-l PEI(i200 MW) 0.64% 87.8 80.8 69.4 7 A-Z PEl (I800 MW) 0.68% 88.4 8L0 68.3 7A-3 PEI (100,000 MW) 0.68% 83.5 70.8 57.l 7 8-1 PEI l-l (PEl-l-Lauric0.6l 86.0 72.8 59.5

Acid) 7 8-2 PEI l-6 (PEl+Stcaric 0.65 881 76.3 65.1

Acid) 7 8-3 PM l-4 (PEl+Tall 0.60% 82.4 62.5 55.l

Acid) 7 C-1 PEI 2-l lPEl+Lauric+ 0.67% 88.9 85.5 78.0

Epi) 7 C-2 PEI 2-7 (PEl+Stearic 0.67% 89.0 84.5 72.3

+Epi) 7 C-3 PEI 2-4 (PEl+Tall+ 0.69% 87.9 85.1 70.8

Epi)

polyamide by reaction in aqueous solution at about 0-50 C. with at least0.8 mole of epichlorohydrin per amino group to yield a watersoluble,thermosetting polyethylenimine-fatty acid-epichlorohydrin resin solublein water as a 15-30 weight percent solution at pH 2.0-7.5 and 25 C.

2. The cellulosic product of claim 1 where the watersolublepolyethylenimine has an average molecular weight of about 5005,000.

3. The cellulosic product of claim 1 where the fatty acid is lauricacid.

4. The cellulosic product of claim 1 where the fatty acid is stearicacid.

5. The cellulosic product of claim 1 where the fatty acid is oleic acid.

6. The cellulosic product of claim 1 where the fatty acid is tall oil.

7. The cellulosic product of claim 2 containing about 0.5-2.5 weightpercent of the polyethylenimine-fatty acid-epichlorohydrin condensationproduct as a sizing agent.

8. The cellulosic product of claim 2 containing about 0.1-2.0 weightpercent of the polyethylenimine-fatty acid-epichlorohydrin condensationproduct as a softening agent.

2. The cellulosic product of claim 1 where the water-soluble polyethylenimine has an average molecular weight of about 500-5,
 000. 3. The cellulosic product of claim 1 where the fatty acid is lauric acid.
 4. The cellulosic product of claim 1 where the fatty acid is stearic acid.
 5. The cellulosic product of claim 1 where the fatty acid is oleic acid.
 6. The cellulosic product of claim 1 where the fatty acid is tall oil.
 7. The cellulosic product of claim 2 containing about 0.5-2.5 weight percent of the polyethylenimine-fatty acid-epichlorohydrin condensation product as a sizing agent.
 8. The cellulosic product of claim 2 containing about 0.1-2.0 weight percent of the polyethylenimine-fatty acid-epichlorohydrin condensation product as a softening agent. 